Fibre optic cable is used to communicate digital and analogue information by the transmission of pulses of light. By necessity, the fibre optic cable must have joints or connections with other fibre optic cable. Signal strength can be weakened by losses at joint or connections due to reflection or absorption of light at the joint between the fibre optic cables. It is desirable to minimize these losses either by minimizing the number of joints in the fibre optic transmission line or by ensuring that any joints or connections are of the highest optical quality.
Normally, two pieces of equipment are interconnected by connecting one end of a short section of fibre optic cable (called a patch cord) to the jack provided on the external surface of one of the pieces of equipment, and by connecting the other end of the patch cord to a patch panel. The patch panel has a housing upon which are secured a plurality of jacks, each of which is optically connected to one end of an individual fibre optic cable which forms part of am multi-fibre optic cable. The multi-fibre optic cable exits from the patch panel and runs to the other piece of equipment or to another patch panel which in turn is connected to the other piece of equipment.
Traditionally, one fibre optic cable is connected to the other fibre optic cable either by physical contact (butt-joining) or by melting them together (fusion).
Butt-joints are made by grinding the end surfaces of the two fibre optic cables to a smooth, convex radius and securing the mating cables so that their respective end surfaces are provided with secure physical contact. Failure to do this may result in the optical connection between the fibre optic cables being broken. Butt-joining is used to attach patch cords to patch panels.
Two fibre optic cables can also be joined by heating their end portions to a plastic or melted state, holding them together in alignment and permitting the fibres to solidify together. This process is usually referred to as fusion or as fusing the fibre optic cables together.
The conventional method for connecting a multi-fibre optic cable to a patch panel is to insert the end of the multi-fibre optic cable into the housing of the patch panel and divide the multi-fibre optic cable into its individual fibres. The fibres are wrapped around a spool within the patch panel housing to allow for additional fibre for making connections in case the end of the fibre is damaged in an initial attempt and to prevent bending of the cable to the extent that the optical fibre breaks. Spools of such type are illustrated in U.S. Pat. No. 4,976,510 issued Dec. 11, 1990 and U.S. Pat. No. 5,231,587 issued Jul. 27, 1993.
Each individual fibre is then optically connected to an external connector attached to the housing of the patch panel either by:
(a) fusing the end of the individual fibre optic cable to a pigtail which in turn is butt-joined to the external connector; or PA1 (b) grinding the end of the individual fibre, attaching a field connector to the fibre and attaching the field connector to a coupler attached to the housing of the patch panel.
As will be appreciated, each process (the butt-joining and the fusion process) requires specific equipment to be used to machine the ends of the fibre optic cable or to soften or melt the ends of the fibre-optic cable while at the same time establishing the proper relative alignment of the fibre optic cables. The equipment is relatively easy to use in a factory environment where energy the plentiful and environmental conditions are easily controlled. In a field environment however, the grinding, heating and aligning steps are more difficult to do well and consume time and energy in the installation process.
Thus there is a need for a patch panel device which is easily used in the field to provide a reliable connection between a patch cord extending from one piece of equipment and a fibre optic cable extending to another piece of equipment or to another patch panel. There is also a need for a connector which will securely retain a fibre optic cable so as to prevent movement of it within a housing to inhibit damage to the fibre optic cable.
It is therefore an object of the present invention to provide a novel connector for fibre optic cable, a novel method of forming the same and a novel adapter for optically coupling a pair of optic fibres.